For the production of many kinds of machine components longitudinal bars are used as starting element, for example in the form of metallic bars or wooden poles. The longitudinal bars are prefabricated at a first production site, stored in a suitable storage and transported to a specific machine for further processing. In the storage many bars are stocked parallel to each other, lying next to each other and on top of each other. For further processing the bars have to be isolated, separately removed from the storage and transported to a processing machine. Different kinds of separating and transportation devices are known, which handle longitudinal bars within a manufacturing process. For transportation for example conveyor lines or rotating spindles are used. For separation the bars may manually or automatically entered into a sorting unit, which is designed to feed only one single bar to the transportation unit. Such separating and transportation devices have to make sure that definitely just one bar proceeds to a processing machine independent of weight, diameter, length, and shape of the bar. In particular for thin bars there is a risk of feeding more than one bar or feed a bar in a false alignment to a processing machine.
In EP 1 110 642 A2 a device for feeding longitudinal bars in the manufacture of melded laths is shown, wherein the bars are first transported by a vertical lift to a gripping unit, which grips the bars separately and dispenses each bar to a conveyor plane. The gripping unit comprises a transport belt along which a plurality of gripping organs are arranged in series. The gripping organs comprise a concave groove for accommodating a single bar and an articulated latch, which closes the groove after the bar has been dropped into the groove. The gripping organ is moved around an axle of the conveyor plane and the latch is opened so that the bar falls from the groove onto a moveable transport plane. The feeding device needs an elaborated mechanism to control the different components and movements to ensure that the bars are handled correctly.
Another bar feeder is disclosed in US 2006/0153666, which comprises a swing member designed to be swingably moved around a rotation shaft located above a guide rail for transportation of the bars. The bars are stored on an oblique chute and guided by several guide elements, which limit the movement of the bars. By gravity the bars roll towards an output pusher, which pushes a single bar from the chute. The bar falls towards the swing member, which is moveable from a blocking position for holding back the bar to a release position for transferring the bar to the guide rail. Again, this is a complicated mechanism, wherein many mechanical parts have to interact so that the bar feeder works properly. Furthermore, the bar feeder is only suitable for bars with a specific diameter because the bars have to fit through gaps defined by the mechanical parts, e. g. the guide elements or the swing member, and also may not be to small so that more than one bar could fit through these gaps.